я так делал
@if (config('app.env') !== 'production')
<!-- Core Template Styles -->
<link rel="stylesheet" href="{{asset('assets/css/main.css')}}">
<link rel="stylesheet" href="{{asset('css/app.css')}}">
@else
<!-- Core Template Styles -->
<link rel="stylesheet" href="{{asset(mix('css/main.css'), true)}}">
<link rel="stylesheet" href="{{asset(mix('css/app.css'), true)}}">
@endif